The present invention relates to cargo tiedown tensioners used to secure cargo during transportation and, more particularly, to tensioners including both a hook for attachment to a fixed point and a pivotably-mounted chain block for releasably engaging a tensioning chain.
Cargo tiedown tensioners are used to secure cargo in aircraft, trains, trucks, ships, and the like, where it is necessary to prevent a shifting of such cargo during acceleration and/or movement of the transportation vehicle. In many applications, there is limited space for the operator to maneuver the tensioner, thereby hindering installation/removal of such device. To increase the ease of installation/removal of the tensioner, certain tiedown tensioners, such as the device disclosed in U.S. Pat. No. 8,646,820, now include a hook wherein the orientation of the hook can be adjusted by the operator. As will be recognized by those skilled in the art, the ability to orient the hook allows the operator to position the release handle of the tensioner in the most appropriate orientation for that particular installation. However, the prior art tiedown tensioners which include a rotatably adjustable hook suffer from the disadvantage that the operator is often required to use both hands to adjust the orientation of the hook. For example, the device disclosed in U.S. Pat. No. 8,646,820 requires the operator to simultaneously apply an axial tension force on opposing sides of the device to overcome a locking spring force before the hook can be reoriented. As already mentioned, the installation space in which the tensioner is installed is often quite limited, thereby rendering a device which may require two hands to re-orient the hook less than desirable.
The prior art discloses various chain tensioning and tiedown devices including the devices shown in U.S. Pat. Nos. 2,848,777, 2,903,767 and 4,850,768. These devices include a pivotably-mounted chain block having an entrance path to receive a tensioned segment of chain, and a blind pocket from which the slack (or free end) of the chain extends. There are, however, a number of problems associated with conventional tiedown devices, including those disclosed in the foregoing patents. In such devices, the precise placement of the chain in the blind pocket is important. If the chain link is not installed properly in the blind pocket (in contact with the bottom of the blind pocket), the force for release is increased in direct proportion to the increase in distance between the contact point and the bottom of the blind pocket. Accordingly, the operator must ensure the proper position of the chain link within the tensioner during securement of the cargo.
Certain applications require tiedown tensioners which are capable of being manually released under loads up to ten thousand (10,000) pounds. Potential energy at the pivot block increases as a function of the load. At the moment of release, potential energy in the tensioned chain is transformed into kinetic energy and transferred to the chain block. This kinetic energy results in the nearly instantaneous rotation of the chain block, such rotation typically being stopped by contact between the chain block and the rigid elements of the tensioner. Because of the nearly instantaneous transfer of the kinetic energy, the operator will likely still have his hand on the release lever, and may therefore be subjected to any kickback movement of the tensioner.
There is therefore a need in the art for a tiedown tensioner having a rotatably adjustable hook which can be operated in confined areas using a single hand. There is a further need in the art for a tiedown tensioner which facilitates the preferred positioning of the tensioning chain within the blind pocket, which minimizes the potential energy for any given load, and which dissipates the kinetic energy in a manner which minimizes the kickback movement of the tensioner.